Data processing system

ABSTRACT

In a data processing system having a primary site and a secondary site, storage systems are connected to each other via a communication line, data update history is recorded in a storage device as a journal in the primary site, and the journal is transferred to the secondary site via the communication line. During such transfer, loads will not concentrate to a specific volume, by switching the volume that stores the journal in the primary site, while, by switching the transfer-destination volume of the journal in the secondary site. With such arrangement, in a data processing system, it is possible to ensure data consistency in a plurality of sites and prevent the system throughput capacity from being deteriorated without applying loads to a host and a network, and without causing load concentration on a specific storage device that is caused as a result of data update or recovery operations.

BACKGROUND OF THE INVENTION

The present invention refers to data processing systems, and moreparticularly to a data processing system that is suitable for use with atechnology to distribute and store journals in a plurality of sites.

The data processing system is demanded to prevent data loss in a storagesystem during disaster or the like. To this end, a technology toduplicate data in a storage system located in a remote place has asignificant meaning. Note that the storage system referred to hereinincludes storage devices such as a storage controller and a disk drive.

A technology to duplicate data stored in a storage system to anotherstorage system is disclosed in U.S. Pat. No. 6,324,654. This patentfurther discloses a technology wherein, upon receipt of a write systemcall, a device driver of the OS of a computer (hereinafter referred toas a “primary host”) incorporated in a first system writes data to alocal data device and stores update log in a write log device, a programof the primary host transfers updated log to a program of a computer(hereinafter referred to as a “secondary host”) incorporated in a secondsystem, and data of a data device of the second system is updated basedon the update log information received by the program of the secondaryhost.

In the above-stated prior art, data stored in respective storage systemsof the primary host and the secondary host is transferred between thetwo hosts. At this time, the hosts are used as transport paths of thedata. Since the data stored in the storage systems are transferred via acommunication link between the hosts, the prior art had problems thatthe CPU loads of the respective hosts, channel loads, and traffics in aline connecting the hosts are increased. Further, the prior art hadanother problem that, since no considerations are given on loadbalancing of the devices that occurs due to log sampling, log writingprocesses and log reading processes concentrate on the write log device.

The present invention has been made to solve above-stated problems ofthe prior art, and an object of the present invention is to provide adata processing system capable of recovering data by sampling dataupdate logs, which is able to assure data consistency in a plurality ofsites without deteriorating its processing capability by giving no loadon hosts and a network, and avoiding centralized loads on a specificstorage device due to data update or recovery.

SUMMARY OF THE INVENTION

A data processing system according to the present invention includes aprimary site and a secondary site, and each of such sites is providedwith a host and a storage system.

Information on a data update stored in a storage system of the primarysite (hereinafter referred to as a “primary storage system”) is storedas a journal (update history). More specifically, the journal is a logof duplicated data copy and metadata that are used for an update.

The primary storage system transfers the journal to a storage system ofthe secondary site (hereinafter referred to as a “secondary storagesystem”) via a communication line connected to the secondary storagesystem. The secondary storage system recovers data stored in thesecondary storage system by using the journal received from the primarystorage system (Recovering data by using a journal shall be referred toas the “journal reflection” hereunder).

In the present invention, since recovery is performed by transferring ajournal, not mere data, to the secondary site, it is possible to quicklyrecover data at no particular point of time upon occurrence of afailure, thus ensuring to guarantee data consistency.

Further, in the present invention, the primary storage systemincorporates a plurality of logical volumes that store journals, andconcentration of logical volumes and accesses in the journal transfersource can be avoided by switching storage logical volumes used at thistime for journal logs, thus ensuring adequate load balancing.

Likewise, in the secondary storage system, concentration of accesses canbe avoided by switching a logical volume of the journal transfer targetthat is used for journal transfer to set a volume different from thelogical volume, thus ensuring adequate load balancing.

It should be noted that the system may be configured such that thejournal transfer can be realized by issuing a request for journaltransfer to the primary storage system from the secondary storagesystem.

In addition, the system may also be configured such that the primaryhost and the secondary host are designed to monitor the status ofstorage system connected to each host based on a program that runs oneach host, and the host in each site instructs data transfer between thestorage systems to the storage system of the site concerned.

According to the present invention described above, there is provided adata processing system capable of recovering data by sampling dataupdate logs. More specifically, the data processing system can assuredata consistency on a plurality of sites, by giving no loads on thehosts and the network, and without causing deteriorated systemprocessing capability, by avoiding centralized loads on a specificstorage device to be caused as a result of data update or recovery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a hardware configuration of a dataprocessing system according to a first preferred embodiment of thepresent invention;

FIG. 2 is a diagram showing a functional configuration of a dataprocessing system according to the first preferred embodiment of thepresent invention;

FIG. 3 is a diagram showing journal group management information;

FIG. 4 is a diagram showing data volume management information;

FIG. 5 is a diagram showing journal meta-information;

FIG. 6 is a diagram showing correlations between a data volume and ajournal volume;

FIG. 7 is a diagram showing an internal structure of a journal data area820 in a primary journal volume;

FIG. 8 is a diagram showing an internal structure of a journal data area820 in a secondary journal volume;

FIG. 9 is a diagram showing switching configuration information of ajournal volume;

FIG. 10 is a flow chart showing outlined processes of a data processingsystem according to the first preferred embodiment;

FIG. 11 is a diagram showing journal process operations according to thefirst preferred embodiment of the present invention;

FIG. 12 is a conceptual diagram for explaining switching of a journalvolume;

FIG. 13 is a flow chart showing a switching process of a primary journalvolume;

FIG. 14 is a flow chart showing a switching process of a secondaryjournal volume;

FIG. 15 is a diagram showing journal process operations according to asecond preferred embodiment of the present invention;

FIG. 16 is a diagram showing journal process operations according to athird preferred embodiment of the present invention; and

FIG. 17 is a diagram showing journal process operations according to afourth preferred embodiment of the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments according to the present inventionwill be described with reference to FIGS. 1 to 17.

First Embodiment

A first preferred embodiment according to the present invention will bedescribed below with reference to FIGS. 1 to 13.

(I) Configuration of Data Processing System

First, a configuration of a data processing system according to thefirst embodiment of the present invention will be described withreference to FIG. 1.

FIG. 1 is a diagram showing a hardware configuration of the dataprocessing system according to the first embodiment of the presentinvention. FIG. 2 is a diagram showing a functional configuration of thedata processing system according to the first embodiment of the presentinvention.

The data processing system of the embodiment allows sites to worktogether to process data. Each of the sites includes a host and astorage system.

Here, a first site is referred to as a “primary site” and a second siteis referred to as a “secondary site”. An example of transferring ajournal from the primary site to the secondary site will be describedbelow. Further, a host that belongs to the primary site shall be calleda “primary host”, a storage system that belongs to the primary siteshall be called a “primary storage system”, a journal to be stored in astorage device of the primary storage system shall be called a “primaryjournal”, and a volume to be stored in the primary journal shall becalled as a “primary journal volume”. The same shall applies to thesecondary site.

Now, as shown in FIG. 1, a primary site 100A includes a primary host110A and a primary storage system 120A, while a secondary host 100Bincludes a secondary host 110B and a secondary storage system 120B, anda management terminal unit 130 is connected to the hosts and thesystems.

The two hosts 110 (i.e., the primary host 110A and the secondary host110B) are computers. Each of the computers includes a processor 111, amain memory 112 and an I/O unit 113. In addition, the computer isspecifically a workstation, a personal computer, a mainframe, or thelike.

Each of the storage systems 120 includes a storage controller 140, oneor more storage devices 121 and a maintenance terminal unit 122. Thestorage device 121 is an auxiliary storage device such as a magneticdisk storage device or an optical disk storage device. However, thesystems 120 may not be provided with the maintenance terminal unit 122.

The storage controller 140 includes a host I/O unit 141, a cache memory142, a disk I/O unit 143, a processor 144 and a control memory 145.

The two hosts are respectively connected to the storage systems via ahost-storage system network 150 such as a local area network (LAN) or astorage area network (SAN). The processor 111 and the main memory 112 ofa host are connected to the host I/O processor 141 of the appropriatestorage system 120 via the I/O unit 113 and the host-storage systemnetwork 150.

The two storage systems are connected to each other via an inter-storagesystem network 160. In general, global networks such as public telephonelines are frequently used for the inter-storage system network 160, andthe networks are often rented on a charged base by communicationservice-providers. Such global networks are frequently used to maintaina certain distance for system safeties (to prevent both sites fromsimultaneous failures), but local networks may be used in a case the twostorage systems are located in a room, a building or adjacent buildings,provided that, however, the present invention is not limited to suchnetwork types.

The management terminal unit 130 is also a computer that has a processoror a main storage device. The management terminal unit 130, the primaryhost 110A, the secondary host 110B, the primary storage system 120A andthe secondary storage system 120B are connected to each other via anetwork 170 such as a LAN or a WAN.

FIG. 2 shows a functional configuration of such data processing systemas stated above.

In each of the storage controller 140, a journal process managementprogram 221, a journal transfer program 222 and a journalacquisition/reflection program 223, which are programs used forcontrolling data transfer between the storage systems 120, are executedon the processor 144. These programs are stored in the control memory145.

The journal process management program 221 manages journal processing(journal acquisition, journal transfer and journal reflection) that isexecuted by each storage system. Such processing will be described indetail later. Further, during the journal-processing phase,communication is performed from time to time between the journal processmanagement programs 221 of the respective storage controllers 140, thusexchanging management information required for the journal processing.

The journal acquisition/reflection program 223 is a program enabling theprocessor 144 to acquire and reflect journals, and the program 223 iscomposed of a journal acquisition program and a journal reflectionprogram.

Further, the storage controller 140 also executes I/O processing to andfrom the storage device 121 based on instructions from hosts, inaddition to processing associated with the journal process managementprogram 221, the journal transfer program 222 and the journalacquisition/reflection program 223.

The storage device 121 has one or more logical storage areas (logicalvolumes) created therein. A logical volume is associated with a physicalstorage area owned by the storage device 121. These logical volumes areused as a data volume area 225 and a journal volume area 227 asdesignated by a user. It should be noted that, in each host 110, anapplication program 211 used by a user or a storage control program 212which executes control of interface with the storage systems are alsoexecuted by the processors 111 owned by the hosts 110. In addition, thejournal processing management program 221 and the storage controlprogram 212 mutually exchange information.

It should also be noted that a data volume, owned by the primary storagesystem 120A, which should be the copy source for data duplication shallbe referred to as the “PVOL”, and a data volume, owned by the secondarystorage system 120B, which should be the duplication target of data tobe stored in the PVOL shall be referred to as the “SVOL.”

A management program 231 that is executed on the management terminalunit 130 manages configuration elements of the data processing systemaccording to the embodiment, or more specifically the program manageshosts 110 or storage systems 120. The management program 231 is storedin the main storage device of the management terminal unit 130.

It should be noted that programs described above are installed in astorage medium owned by each devices by using a mobile medium such as acompact disk or a magnet-optical disk, or via the network 170.

(II) Data Structure Used for the Data Processing System

Next, a data structure to be used for the data processing systemaccording to the embodiment will be described with reference to FIGS. 3to 9.

FIG. 3 is a diagram showing journal group management information. FIG. 4is a diagram showing data volume management information. FIG. 5 is adiagram showing journal meta-information. FIG. 6 is a diagram showingcorrelations between a data volume and a journal volume. FIG. 7 is adiagram showing an internal structure of a journal data area 820 in aprimary journal volume. FIG. 8 is a diagram showing an internalstructure of a journal data area 820 in a secondary journal volume. FIG.9 is a diagram showing switching configuration information of a journalvolume.

The journal group management information is information used formanaging a journal group and is stored in the control memories 145 ofstorage system 120.

Here, the term “journal group” implies a pair of volumes in which a datavolume and a journal volume that stores a journal of the data volume areassociated with each other.

The journal group management information contains, as shown in FIG. 3, ajournal group ID 410, a latest journal sequence number (No.) 420, datavolume information 430, journal volume information 440 and transfergroup information 450.

The journal group ID 410 is an identifier which uniquely identifies ajournal group. The latest journal sequence number 420 is the latestnumber created among consecutive numbers to be created for journals inthe journal group.

The data volume information 430 contains data volume managementinformation 431 of data volumes contained in the journal group. Detailsof the data volume management information will be described later.

The journal volume information 440 contains information on journalvolumes and journal volume IDs for storage 444 which are contained inthe journal group. Information of each journal volume contains a volumeID 441 identifying the volume, a first journal sequence number 442 whichindicates the sequence number of the oldest journal among journalsstored in the journal volume, and a last journal sequence number 443which indicates the sequence number of the newest journal.

The journal volume ID for storage 444 is provided to indicate a journalvolume in which a subsequent journal is stored, when a plurality ofjournal volumes are available in a journal group. In the primary storagesystem 120A, the journal volume ID 444 implies a journal volume that isused to store journal during a journal acquisition process, while in thesecondary storage system 120B, the journal volume ID 444 implies ajournal volume that is used as a transfer target of a journal during ajournal transfer process. It should be noted, however, that, when onlyone journal volume exits, an ID of a journal volume that is used forstorage and transfer is set in the journal volume ID for storage 444.

The transfer group information 450 contains a journal group ID 451 whichis an identifier of a journal groups to be paired, a transfer-completedjournal sequence number 452 which indicates to which journal thetransfer to the secondary storage system is completed, areflection-completed journal sequence number 453 which indicates towhich the journal reflection process is completed in the secondarystorage system 120B, and a pair status information 454 which indicatesthe status of transfer groups. It should be noted that a journal whichhas a sequence number subsequent to the transfer-completed journalsequence number 452 becomes the oldest journal. The secondary storagesystem (the primary storage system in the second and the fourthembodiment) specifies and uses a journal volume that contains the oldestjournal as the journal volume. When a journal volume for transfer and ajournal volume for storage coincide with each other, the journal volumecontaining the oldest journal and the journal volume indicated by thejournal volume ID for storage 444 coincide with each other. On the otherhand, as a result of a switching process, or if a journal volume fortransfer and a journal volume for storage are differentiated from eachother in advance, the journal volume containing the oldest journal andthe journal volume indicated by the journal volume ID for storage 444 donot coincide with each other. The same applies to the secondary storagesystem 120B.

Here, the term “transfer group” implies that a transfer source journalgroup and a transfer target journal group are associated with each otherand paired.

The reflection-completed journal sequence No. 453 is notified to thejournal process management program 221 of the primary storage system120A from the journal process management program 221 of the secondarystorage system 120B.

The pair status 454 includes. “PAIR” which means that all data volumesavailable in a journal group are in a duplicated status and “COPY” whichmeans that one or more data volumes available in a journal group areexecuting a differential copy (the differential copy will be describedlater). Further, there are two more statuses: a status of “SUSPEND”which means that all data volumes are in a suspend status withoutexecuting duplication and consistency is maintained for all data withinthe journal group; and a status of “SUSPEND-E” which means a statuswhere consistency is not maintained in the journal group.

The data volume management information 431 is information used formanaging a data volume, and as shown in FIG. 4, the information containsa volume ID 510 which identifies a data volume in a storage system, andpair volume information 520 which is information on paired data volumes.

The pair volume information 520 contains a storage system ID 521, a datavolume ID 522 which identifies paired data volumes, a pair status 523which shows a duplication status, an effective flag of differential bitmap 524, and a differential bit map 525.

The storage system ID 521 is an identifier of a storage system in whichpaired data volumes exist, and the data volume ID 522 is a volumeidentifier in the storage system. A data volume can be uniquely definedby combining the storage system ID 521 and the data volume ID 522.

The pair status 523 implies either status of the “PAIR” in which datavolumes are in a duplicated status (a status where data consistency ismaintained within a volume), the “COPY” which means that one or moredata volumes available in a journal group are executing a differentialcopy, or the “SUSPEND” in which copying processes are discontinued to bein the suspend status due to blockage of a volume, a path, etc.

The effective flag of differential bit map 524 indicates whether a valueof a differential bit map is effective. The differential bit map 525 isinformation that indicates an area in which the PVOL and SVOL data aredifferent from each other. A data volume area is divided into aplurality of areas, and, if a data volume is updated under the SUSPENDstatus, a bit indicating the updated area is turned on. Afterestablishing the SUSPEND status, a pair can be recovered to a duplicatedstatus by duplicating only the bit-on area based on a bit map in whichOR is removed from the respective differential bit maps 525 of the PVOLand the SVOL (differential copying). Copy transfer volume can be reducedby executing the differential copying. With the differential copying,the area in which copying is completed turns off the bit, and when allbits are turned off, then the differential copying is completed.Further, when a pair is created, the entire area of the PVOL can becopied to the SVOL by turning on all differential bit maps and applyingdifferential copying (initial copying).

The journal meta-information is management information used to associatedata with journals, and, as shown in FIG. 5, the meta-informationcontains data volume information 710 and journal information 720.

The data volume information 710 contains update time 711 which indicatesdata update time, storage data volume offset in journal group 712 whichindicates a data volume whose data is to be updated falls on which datavolume in a journal group, and a data storage address 713 whichindicates a first address in which data on a data volume is stored.

The journal information 720 contains a journal data storage address 721which indicates a first address in which journal data on a journalvolume is stored, data length 722 of journal data, and a journalsequence number 723 which is one of serial numbers of journals in ajournal group that is assigned when a journal is acquired.

The data volumes and the journal volumes that are associated with eachother by the journal meta-information are shown in FIG. 6.

In general, the PVOL, the SVOL and a journal volume are each managed ona predetermined logical block basis (e.g., 512 KB). A logical blockaddress (hereinafter referred to as an “LBA”) is given to each of thelogical blocks.

A primary journal volume 267A has a meta-data area 810 and a journaldata area 820. In the meta-data area 810, the journal data 821Adescribed earlier, or a copy of data 831A that is written in the PVOL bya write command, is stored. In the meta-data area 810, the meta-data811A described earlier is stored. The meta-data contains a data storageaddress 812A of update data, and a storage address 813A of journal data.

A secondary journal volume 267B also has a meta-data area 810 and ajournal data area 820 as is the case with the primary journal volume267A. In the meta-data area 810, meta-data 811B that is transferred froma meta-data area of a primary journal volume is stored. In the journaldata area 820, journal data 821B (associating with meta-data) that istransferred from a journal data area of the primary journal volume 267Ais stored.

The meta-data 811B has information on data update that is performed inthe PVOL, and address information 813B of the meta-data 811B indicatesan address of the associated journal data 821B. Further, by copying thejournal data 821B to an address of an SVOL 266 associated with theaddress 812B from the journal data area 820 of the secondary journalvolume 267B, it is possible to reflect the update made in a PVOL 265 inthe SVOL 266.

It is possible that each address is expressed by an LBA and data lengthis represented by the number of logical blocks. In addition, a locationin which data is stored can be represented by a difference (offset) froma base address (first LBA) of an area in which the data is stored(journal data area or meta-data area). With the embodiment, data lengthof meta-data is set to a given length (64 bytes, for example), but datalength of journal data is not constant since it depends on data to beupdated by a write command.

When a journal group is defined, each of the storage systems 120 setsthe meta-data area 810 and the journal data area 820 for the journalvolume 267 to be set. More specifically, the first LBA and the number ofblocks of each area are set.

Next, an internal structure of the journal data area 820 in a primaryjournal volume will be described.

The journal data area 820 contained in the primary journal volume isdivided into a journal storage completed area 910 in which journal datais stored, and a purge completed area 920 in which journal data is notstored, or otherwise, journal data that can be purged is stored. Thepurge completed area 910 is an area that is enabled to release journaldata stored therein following the transfer to the journal data to thesecondary site, and the area can be used for storing new journal data ofthe PVOL 625.

FIG. 7 shows a status where a journal data area 900A and a journal dataarea 900B are stored in separate logical volumes respectively.

In the journal data area 900A, a journal with a first sequence number involume 931A up to a journal with a last journal sequence number involume 932A are stored, while in the journal data area 900B, a journalwith a first sequence number in volume 931B up to a journal with a lastsequence number in volume 932B are stored. When a journal is stored, itis always written in the first place in a volume.

A journal volume is repeatedly used in the same way as it is done for acyclic buffer. More specifically, when the last logical block of ajournal is used up, the first logical block is then used again. Itshould be noted, however, when a plurality of journal volumes arecontained in a journal group, if the last logical block of a journal isused up, the first logical block of the subsequent journal volume isused. When the last logical block of the last journal volume is used up,then use of the first logical block of the first journal volume isresumed. It should be noted that, before the last logical block of ajournal volume is used, it may be possible to switch an intermediatelogical block over to the first logical block of the next journalvolume. Switching of a storage target of a journal over to the nextjournal volume is called a “journal volume switching process.”

In FIG. 7, after the journal area 900A is used up to the first journalsequence number in volume 931A, the journal volume is switched over tothe first journal of the journal data area 900B. To that end, the firstjournal sequence number in volume 931A and the last journal sequencenumber in a volume 932B are uninterrupted. The journal volume switchingprocess will be described in detail later.

A storage-completed sequence number 911 indicates the latest journal. Ajournal to be acquired next is given a journal sequence number having avalue that is obtained by adding 1 to the storage-completed sequencenumber 911 and is stored in a purge area of the journal data area 900B.Here, a journal volume for storage implies a journal volume that has thejournal data area 900B. A journal with a sequence number obtained byadding 1 to a transfer-completed sequence number 921 is the oldestjournal. If the transfer-completed sequence number 921 is equal to thestorage-completed sequence number 911, this means that the journal isempty.

Next, an internal structure of the journal data area 820 in thesecondary journal volume will be described.

As shown in FIG. 8, the journal data area 820 contained in the secondaryjournal volume is divided into: a purge-completed area 1030 in whichjournal data that is already used for reflection of the journal to theSVOL 626 is stored (or, the journal data is not stored); area underreflection 1020 in which the journal data that is subject to journalreflection to the SVOL 626; a transfer completed area 1011 in whichjournal data that is the target for journal reflection and for journaltransfer from the primary journal volume has been completed is stored;and area under transfer 1010 in which journal data under transfer fromthe primary journal volume is stored.

In a journal data area 1000A, a journal with a first sequence number involume 931C up to a journal with a last journal sequence number involume 932C are stored, while in the journal data area 1000B, a journalwith a first sequence number in a volume 931D up to a journal with alast sequence number in volume 932D are stored. Here, journal volumeswitching occurs after the first sequence number in volume 931C has beenstored, and therefore, the first sequence number in volume 931C and thejournal with a last sequence number in volume 932D are uninterrupted.

A sequence number to be transferred 1012 indicates a first journalsequence number of a journal that is under transfer from the primaryjournal volume. Journals with the sequence number to be transferred 1012and subsequent sequence numbers are transferred next and stored in apurge area of the journal data area 1000B. Here, a volume ID to bestored in the journal volume IDs for storage 444 shown in FIG. 3indicates a journal volume having the journal data area 1000B which is atarget volume for transfer. A transfer completed sequence number 1013indicates a sequence number of a journal whose transfer process iscompleted last.

A sequence number to be reflected 1021 indicates the first sequencenumber of a journal targeted for journal reflection, or otherwise, thenumber indicates a sequence number of a journal whose reflection processis completed following the reflection-completed sequence number 1022.

Next, journal volume switching configuration information will bedescribed.

The journal volume switching configuration information is managementinformation used to switch journal volumes.

With the process according to the present invention, it is possible toswitch journal volumes in both the primary site and the secondary site.

The journal volumes of the primary site 100A is switched by switchingthe logical volumes that are used for storing present-time journals inorder to balance loads on (source) logical volumes used for storing andon logical volumes used for data transfer by present-time journals.

The journal volumes of the secondary site 100B is switched by switchingthe logical volumes that are used for transfer in order to balance loadson (target) logical volumes used for transfer and on logical volumesused for data recovery by present-time journals.

As shown in FIG. 9, the journal volume switching configurationinformation comprises effective flag of switching judgment 1110,judgment information 1120 and operation under out-of-conditioncircumstances 1130.

The effective flag of switching judgment 1110 is a flag for executingswitching judgment process or not. If no journal volume switchingjudgment is executed, the effective flag of switching judgment 1110 isturned OFF.

Although the switching judgment at the primary site 100A may beperformed at given timing, it is effective to performed the switchingjudgment when, after transfer of a journal of a certain volume iscompleted, a journal volume in which a journal to be transferred next isstored is used as a volume which stores a present-time journal. Theswitching judgment at the secondary site 100B can also be performed atgiven timing, but it is effective to perform the switching judgmentwhen, after data reflection by a journal of a certain volume iscompleted, a journal volume in which a journal to be used for thereflection next is stored is used as a transfer target volume. Here,attention should be paid to the fact that the journal data has asequential structure as used in FIGS. 7 and 8. Such switching judgmentwill be described in detail later.

The judgment information 1120 contains set values concerningnon-transferred journal volume, and set values concerning timedifference between the time when the oldest journal amongnon-transferred journals is updated and the time when judgment is made.Each set value contains an effective flags 1121 and 1123 to make thejudgment criteria effective or not, and threshold conditions 1122 and1124 for performing switching of volumes for storage.

For example, for the primary journal volume, when non-transferredjournal volume is small, loads of journal processing would notconstitute a big problem even if a logical volume used for storing apresent-time journal coincides with a logical volume used for transfer.On the other hand, for the secondary journal volume, when a journalvolume to be recovered is small, loads of journal processing would notconstitute a big problem even if a logical volume used for data recoveryby a present-time journal coincides with a logical volume used fortransfer.

Consequently, for the case of the primary journal volume, the thresholdconditions 1122 would include that non-transferred journal volume(difference between the storage-completed sequence number 911 and thetransfer-completed sequence number 921) should exceed the presetthreshold value, while for the case of the secondary journal volume, thethreshold conditions 1124 would include that non-transferred journalvolume time difference (difference of time between the update time ofthe journal with a sequence number obtained by adding 1 to a transfercompleted sequence number 921 and the time when a judgment is made)should exceed the preset threshold value. Further, for the case of thesecondary journal volume, the threshold conditions 1122 may include thatthe non-reflected journal volume (difference between the transfercompleted sequence number 1013 and the reflection-completed sequencenumber 1022) should exceed the preset threshold value, or the thresholdconditions 1124 may include that the non-reflected journal timedifference (difference of time between the update time of the journalwith a sequence number obtained by adding 1 to a reflection-completedsequence No. 1022 and the time when a judgment is made) should exceedthe preset threshold value.

In such cases, for the primary journal volume, switching of journalvolume for storage is executed, while for the secondary journal volume,switching of volume for transfer is executed.

In the operation under out-of-condition circumstances 1130, systemoperations for a situation that does not satisfy the conditions aredescribed. Operations for a situation that does not satisfy theconditions include: for the primary journal volume, (1) journal transferis interrupted, or (2) journal transfer is executed by using a journalvolume that is used for storing the journal; or, for the secondaryjournal volume, (1) journal reflection is interrupted, or (2) journalreflection is executed by using a journal volume which is used as thetransfer target.

In the primary site 100A, the journal switching configurationinformation is set by a user, when a journal group and the like are set,via the management terminal unit 130 or GUI of the maintenance terminalunit 122, and is then stored in the control memory 145. In the secondarysite 100B, the journal switching configuration information is set in thesimilar way, and the information is stored in the control memory of thesecondary storage system 120B.

(III) Outlined Processes of Data Processing System

(III-1) Outlined Processes of Data Processing System

First, outlined processes of a data processing system according to thefirst preferred embodiment of the present invention will be describedwith reference to FIG. 10.

FIG. 10 is a flow chart showing outlined processes of a data processingsystem according to the first embodiment.

First, a user enters a pair generation command to a storage system byusing a graphical user interface (GUI) of the host 110, the controlterminal unit 130 or the maintenance terminal unit 122 (Step 301).

The pair generation command associates the PVOL 625 of the primarystorage system 120A which will be the copy source for data duplicationwith the SVOL 626 of the secondary storage system 120B which will be theduplication target of data to be stored in the PVOL 625 so as to formthem into a pair.

Then, the journal process management program 221 of each site is used tocontrol the primary site 100A so that a volume to store a journalassociated with the PVOL 625 designated in the storage system 120A maybe allocated, and to control the secondary site 100B so that a journalvolume to store a journal associated with the SVOL 626 designated in thesecondary storage system 120B may be allocated (Steps 302 and 303).

In the primary site 100A, a journal group is formed by the PVOL 625 andthe journal volume area 627A that is assigned to the PVOL 625, while inthe secondary site 100B, a journal group is formed by the SVOL 626 andthe journal volume area 627B that is assigned to the SVOL 626. Anaggregate of a plurality of volumes can be assigned to a journal volumewhen the journal group is formed.

The pair generation command also associates a journal group of the PVOL625 with a journal group of the SVOL 626 to create a transfer group(Step 304). Journal volume switching information may be set when thejournal group is set. The journal volume switching setting will bedescribed in detail later.

It should be noted that, when a journal group is formed, assignment ofdata volume is not limited to a single data volume, but an aggregate ofa plurality of data volumes may be assigned. Since data is updated inthe aggregate of SVOLs in a similar way of updating data in theaggregate of the PVOLs, data consistency is maintained in the aggregateof the data volumes.

Next, after a transfer group is formed, journal processes are executed(Step 305). The journal processes imply journal acquisition, journaltransfer, and journal reflection. The journal acquisition is started inthe primary storage system 120, when the primary storage system receivesfrom a use a command instructing acquisition of a journal (hereinafterreferred to as the “journal acquisition start command”). The journalprocesses will be described in detail later.

On the other hand, data that had been stored in the PVOL 625 before thejournal acquisition is started will not be transferred to the secondarystorage system even when the journal transfer is started. It isnecessary to independently copy such data (herein after referred to asthe “initial data”) to the SVOL 626 from the PVOL 625. A process to copythe initial data is called “initial copying.” In the embodiment, initialcopying which transfers the initial data to the SVOL 626 from the PVOL625 is executed (Step 306). The initial data is transferred from thefirst area of volumes up to the last area of volumes in the PVOL 625.

(III-2) Detailed Journal Processes

Next, journal processes will be described in detail with reference toFIG. 11.

FIG. 11 is a diagram showing journal process operations according to thefirst embodiment of the present invention.

The storage systems 120A and 120B execute the journal process managementprogram 221 to control journal processes.

The primary storage system 120A executes the journal acquisition program623 out of the journal acquisition/reflection program 223. The primarystorage system 120A, by executing the journal acquisition program 623,stores a duplicated copy of data to be written to the PVOL 625 asjournal data. In addition, the primary storage system 120A also storesmeta-data in the journal volume area 627A as part of journals. Theabove-stated processes constitute the journal acquisition processes.

On the other hand, the secondary storage system 120B executes journalreflection processes by executing the journal reflection program 624 outof the journal acquisition/reflection program 223. The journalreflection program 624 recovers data based on journals stored in thejournal volume area 627B and reflects data updated in the PVOL 625 inthe SVOL 626.

FIG. 11 shows processes wherein the above-stated processes are executedwith the system illustrated in FIG. 2.

Upon starting journal acquisition processes of the PVOL 625, the primarystorage system 120A creates a journal according to writing (anarrow-headed line 601) from the primary host 110A to the PVOL 625, andstores the journal thus created in the journal volume area 627A (anarrow-headed line 602). Here, the journal acquisition program acquiresinformation such as a latest journal sequence number and a journalvolume ID for storage from journal group management information storedon the control memory 145 of the primary storage system 120A, determinesthe target for journal storage, and creates meta-data information.

The secondary storage system 120B executes the journal processmanagement program 221, and acquires information related to journalcreation status (for example, capacity of a journal in a journal volume,the oldest time of journals, etc.) (an arrow-headed line 603).

The secondary storage system 120B executes the journal processmanagement program 221, and issues a request for journal transfer to thejournal transfer program 222 of the secondary storage system 120Baccording to entry of instruction by a user via a GUI or a predeterminedschedule (for example, at a time when a certain volume of journals isstored in a journal volume in the primary storage system 120A, atregular periods, etc.) (an arrow-headed line 604).

The request for journal transfer contains a journal to be copied (whichmay be a plurality of journals), a journal volume in which theabove-stated journal is stored, information designating the storagesystem 120 (the primary storage system 120A here) which has theabove-stated journal volume, and information designating a journalvolume in which the copied journal is stored. Such information iscreated based on the information that the journal process managementprogram 221 has acquired from the journal management information on thecontrol memory 145.

The journal transfer program 222, upon receiving a request for journaltransfer, issues a read command to the primary storage system 120A (anarrow-headed line 605). The primary storage system 120A, upon receivingthe read command, transmits a journal designated by the read command tothe secondary storage system 120B (an arrow-headed line 606).

An area of a journal volume, in which the journal that is transmitted tothe primary storage system 120B is stored, of the primary storage system120A is purged or cleared, enabling storage of a new journal. It shouldbe noted that the purging is not needed to be executed immediately afterthe transmission. Purging may be executed periodically, or may be doneaccording to a user's instruction.

The secondary storage system 120B, upon receiving a journal, stores thereceived journal in the journal volume area 627B that is designated bythe request for journal transfer.

Thereafter, the journal process management program 221 of the secondarystorage system 120B issues a request for journal reflection to thejournal reflection program 624 of the secondary storage system 120B (anarrow-headed line 607). The journal reflection program 624, uponreceiving the request for journal reflection, recovers data in the SVOL626 based on the journal of the journal volume area 627B (anarrow-headed line 608). It should be noted that the area in which thejournal used for recovery is purged, enabling storage of a new journal.

(III-3) Journal Volume Switching Processes

Next, journal volume switching processes will be described withreference to FIGS. 12 to 14.

FIG. 12 is a conceptual diagram explaining switching of a journalvolume. FIG. 13 is a flow chart showing a switching process of a primaryjournal volume. FIG. 14 is a flow chart showing a switching process of asecondary journal volume.

As already stated in the above, with the present invention, switching ofjournal volume is executed to reduce system loads by avoiding thatlogical volumes used for journal storage, journal reflection and journaltransfer become identical in the process of transferring the journals tothe secondary site 100B from the primary site 100A.

Now, as shown in FIG. 12, it shall be assumed that a logical volume PA,a logical volume PB and a logical volume PC are available in the primarysite 10A, wherein the logical volume PB is used for storing a journal,and the logical volume PA is used for transfer as the transfer sourcelogical volume.

It shall also be assumed that, for the order of journals, those locatedat the upper part of a volume is older, and the last journal of thelogical volume PA is continuously connected to the first journal of thelogical volume PB.

Now, when transfer of journals in the logical volume PA is completed,the next step will be transfer of journals in the logical volume PB, andat this time, a logical volume for storing journals will be switched tothe logical volume PC from the logical volume PB.

Further, it shall be assumed that a logical volume SA, a logical volumeSB and a logical volume SC are available in the secondary site 110B,wherein the logical volume SC is used reflecting a journal, and thelogical volume SA is used for transfer as the transfer target logicalvolume.

It shall also be assumed that, for the order of journals, those locatedat the upper part of a volume is older, and the last journal of thelogical volume SC is continuously connected to the first journal of thelogical volume SA.

In such a case, when reflection of journals in the logical volume SC iscompleted, the next step will be reflection of journals in the logicalvolume SA, and at this time, the target logical volume for transferringjournals will be switched to the logical volume SB from the logicalvolume SA.

In the above, an example wherein switching is carried out at such timingthat all journals in a logical volume for journal transfer and a logicalvolume for journal reflection are transferred or reflected is shown.However, switching of journal volumes may be executed following aswitching command that is entered by a user. Further, the switching maybe executed periodically or at predetermined hours. Furthermore, theswitching may be carried out only when predetermined conditions aresatisfied via an interface of the host 110, the management terminal unit130 or the maintenance terminal unit 122.

In addition, in the primary site 100A, the switching may be executed atsuch timing that accepts a command for requesting journal transfer asshown by the arrow-headed line 605 in FIG. 11. Alternatively, in thesecondary site 100B, the switching may be executed at such timing ofinitiating journal transfer.

More specifically, in the primary site 100A, when there are a pluralityof primary journal volumes, such switching of journal volume can berealized by controlling the balance between the storage-completedjournal sequence number 911 and the transfer-completed journal sequencenumber 921 shown in FIG. 7, thus distinguishing a journal volume to beused for journal acquisition from a journal volume to be used forjournal transfer.

Further, in the secondary site 100B, when there are a plurality ofsecondary journal volumes, it is possible to distinguish a journalvolume to be used for journal reflection from a journal volume to beused for journal transfer by controlling the balance between thereflection-completed journal sequence number 1022 and the journalsequence number to be transferred 1012.

It should be noted that, in the primary site 100A, when a journal whichis subjected to journal transfer (hereinafter referred to as a“non-transferred journal”) is not in a volume except a journal volumethat is used for journal acquisition (more specifically, when the lastjournal sequence number in volume 932B of a journal volume for storageis a number that is obtained by adding 1 to the transfer completedjournal sequence number 921), if switching of the journal volume forstorage is not executed, then journal acquisition and journal transferwill be performed for one and the same journal volume.

Next, primary journal volume switching processes will be describedaccording to the flow of a flow chart illustrated in FIG. 13.

When journal transfer is executed, a flag of journal volume switchingjudgment is checked (Step 1201).

If the switching judgment is not effective, then the journal transfer isexecuted (Step 1208). If the switching judgment is effective, a check ismade as to whether any non-transferred journal exists in a journalvolume except a journal volume for storage (Step 1202). If anynon-transferred journal exists, the journal transfer of the journalvolume is executed (Step 1208). If any non-transferred journal does notexist, a check is made as to whether a judgment based on non-transferredjournal volume is effective and the judgment satisfies thresholdconditions (Step 1203). If the judgment is effective and satisfies theconditions, then the journal volume for storage is switched to thesubsequent journal volume (Step 1207) and journal transfer is executed(Step 1208). If the judgment of journal volume is ineffective or doesnot satisfy the conditions, a check is made as to whether a judgmentbased on time difference between the oldest update time of thenon-transferred journal and present time is effective and the judgmentsatisfies the threshold conditions (Step 1204). If the judgment iseffective and satisfies the conditions, then the journal volume forstorage is switched to the subsequent journal volume (Step 1207), andjournal transfer is executed (Step 1208). If the time differencejudgment is ineffective or does not satisfy the conditions, the presetinformation is reflected (Step 1205), and journal transfer is executedby using a journal volume for storage (Step 1208), or journal transferis interrupted until the next request for journal transfer is issued(Step 1206). When the journal volume for storage is switched in Step1207, the storage controller 140 of the primary storage system 120Are-writes the ID of a journal volume for storage of journal groupmanagement information stored in the control memory 145 to informationindicating a new switching-destination journal volume.

Next, secondary journal volume switching processes will be describedaccording to the flow of a flow chart illustrated in FIG. 14.

When journal reflection is executed, a flag of journal volume switchingjudgment is checked (Step 1301). If the switching judgment is noteffective, then the journal reflection is executed (Step 1308). If theswitching judgment is effective, a check is made as to whether anynon-reflected journal exists in a journal volume except a journal volumefor storage (Step 1302). If any non-reflected journal exists, thejournal reflection of the journal volume is executed (Step 1308). If anynon-reflected journal does not exist, a check is made as to whether ajudgment based on non-reflected journal volume is effective and thejudgment satisfies threshold conditions (Step 1303). If the judgment iseffective and satisfies the conditions, then the transfer-destinationjournal volume is switched to the subsequent journal volume (Step 1307),and the journal reflection is executed (Step 1308). When thetransfer-destination journal volume is switched in Step 1307, thestorage controller 140 of the secondary storage system 120B re-writesthe ID of a journal volume for storage of journal group managementinformation stored in the control memory 145 to information indicating anew switching-destination journal volume. If the judgment of journalvolume is ineffective or does not satisfy the conditions, a check ismade as to whether a judgment based on time difference between theoldest update time of the non-reflected journal and present time iseffective and the judgment satisfies the threshold conditions (Step1304). If the judgment is effective and satisfies the conditions, thenthe transfer-destination journal volume is switched to the subsequentjournal volume (Step 1307), and the journal reflection is executed (Step1308). If the time difference judgment is ineffective or does notsatisfy the conditions, the preset information is reflected (Step 1305),and journal reflection is executed by using a journal volume for storage(Step 1305), or journal reflection is interrupted until the next requestfor journal reflection is issued (Step 1306).

Second Embodiment

Hereinafter, a second preferred embodiment according to the presentinvention will be described with reference to FIG. 15.

FIG. 15 is a diagram showing journal process operations according to thesecond embodiment of the present invention.

In the journal processes according to the first embodiment, the journaltransfer process is performed such that the secondary storage system120B issues a read command requesting the primary storage system 120A toexecute journal transfer as shown in FIG. 11 (the arrow-headed line605). In the second embodiment, journal transfer is executed in such away as that the primary storage system 120A issues a write command tothe secondary storage system 120B, not in such a way as that the primarystorage system 120A waits for a read command issued by the secondarystorage system 120B.

First, in the primary site 100A, journal acquisition for updating thePVOL data (an arrow-headed line 601) is carried out in the way similarto that of the first embodiment (an arrow-headed line 602). The journalprocess management program 221 of the primary storage system 120A issuesa request for journal transfer to the journal transfer program 222 (anarrow-headed line 1404). The journal transfer request contains a journalvolume in which a journal to be transmitted to the storage system 120Bis stored, information designating the storage system 120B, informationdesignating a journal volume which should store the above-stated journalin the storage system 120B, etc. Such information is acquired fromjournal group management information stored in the control memory 145.

The journal transfer program 222, upon receiving the request for journaltransfer, transmits a journal designated by issuing a write command tothe secondary storage system 120B to the secondary storage system 120B(an arrow-headed line 1406). The secondary storage system 120B storesthe journal received as a write command from the primary storage device120A in the area of the secondary journal volume designated by thecommand.

Thereafter, journal reflection (Step 608) in the secondary site 100B iscarried out in the way similar to that of the first embodiment. Inaddition, journal volume switching in the second embodiment is carriedout in the way similar to that of the first embodiment.

Third Embodiment

Next, a third preferred embodiment according to the present inventionwill be described with reference to FIG. 16.

FIG. 16 is a diagram showing journal process operations according to thethird embodiment of the present invention.

The data processing system of the embodiment differs from that of thefirst preferred embodiment in, as shown in FIG. 16, that a journalprocess management program 1521 is not contained in the storage systems120, but in the hosts 110. The journal process management programs 1521execute communication with each other via a communication line thatconnects the primary host 110A and the secondary site 110B.

First, in the primary site 100A, journal acquisition for updating thePVOL data (the arrow-headed line 601) is carried out in the way similarto that of the first embodiment (the arrow-headed line 602).

The primary host 110A acquires information concerning journal creationstatus (e.g., capacity of a journal) from journal volume managementinformation stored in the control memory 145 of the primary storagesystem 120A by executing the journal process management program 1521 andissuing a given command (hereinafter referred to as the “journalcreation status acquisition command”) (an arrow-headed line 1509).

The information concerning journal creation status acquired by theprimary host 110A is notified to the secondary host 110B (anarrow-headed line 1503)

The secondary host 110B executes the journal process management program1521 and issues a request for journal transfer, according to an entrydesignated by a user via a GUI or predetermined schedule (for example,when journals exceeding a given amount are stored in the primary storagesystem 120A, or at a regular period of time) to the primary storagesystem 120B (an arrow-headed line 1504).

The request for journal transfer contains a journal to be copied, ajournal volume in which the journal is stored, information designatingthe storage system 120 which has the journal volume, and informationdesignating a journal volume in which the copied journal is to bestored.

The secondary storage system 120B, upon receiving the request forjournal transfer, issues a read command to the primary storage system120A by executing the journal transfer program 222. The primary storagesystem 120A, upon receiving the read command, transmits the journaldesignated by the read command to the secondary storage system 120B (thearrow-headed line 606). The area in which the journal transmitted to thesecondary storage system 120B is purged or cleared, thus enabling theuse for storing a new journal.

The secondary storage system 120B, upon receiving the journal, storesthe received journal in the journal volume area 627B that is designatedby the request for journal transfer.

Thereafter, the secondary host 110B issues a request for journalreflection to the secondary storage system 120B (an arrow-headed line1507).

The secondary storage system 120B, upon receiving the request forjournal reflection, executes the journal reflection program 624 andrecovers data from the journal volume area 627B to the SVOL 626 (anarrow-headed line 608). The area in which the reflection-completedjournal is stored is purged, thus enabling the use for storing a newjournal.

The journal volume switching in the embodiment is carried out in a waysimilar to the journal volume switching in the first embodiment.

Fourth Embodiment

Next, a fourth preferred according to, the present invention will bedescribed with reference to FIG. 17.

FIG. 17 is a diagram showing journal process operations according to thefourth embodiment of the present invention.

The data processing system of the embodiment differs from that of thefirst embodiment in the point that, in the journal transfer process asshown in FIG. 17, the primary storage system 120A does not wait for aread command from the secondary storage system 120B, but the system 120Aissues a write command to write data to the secondary storage system120B. In addition, the data processing system of the embodiment alsodiffers from that of the first embodiment in the point that a journalprocess management program 1621 is executed not on the storage systems120, but on the hosts 110. Further, the data processing system alsodiffers from that of the first embodiment in the point that thesecondary storage system 120B does not execute the journal reflection,but the secondary host 110B reads a journal to be used for recovery fromthe secondary journal volume area 627B and recovers data of the SVOL626. In the embodiment, the journal reflection program is executed onthe secondary host 110B.

With the embodiment, a general storage device that has no specialfunctions can be used for the secondary storage system 120B, since theprincipal unit to execute journal transfer is the primary storage system120A and journal reflection is executed by the secondary host 110B.

In the primary site 100A, journal acquisition (the arrow-headed line602) for updating the PVOL data (the arrow-headed lien 601) is executedin a way similar to that of the first embodiment.

The primary host 110A acquires information concerning journal creationstatus (e.g., capacity of a journal) from journal group volumemanagement information stored in the control memory 145 of the primarystorage system 120A by executing the journal process management program1621 and issuing a journal creation status acquisition command (anarrow-headed line 1609).

The information concerning journal creation status acquired by theprimary host 110A is notified to the secondary host 110B (anarrow-headed line 1603).

The primary host 110A executes the journal process management program1521 and issues a request for journal transfer, according to an entrydesignated by a user via a GUI or predetermined schedule (for example,when journals exceeding a given amount are stored in the primary storagesystem 120A, or at a regular period of time) to the primary storagesystem 120A (an arrow-headed line 1604).

The request for journal transfer contains a journal volume in which ajournal to be transmitted to the secondary storage system 120B isincluded, information designating the storage system 120B, informationdesignating the journal, etc.

The primary storage system 120A, upon receiving the request for journaltransfer, transmits the designated journal to the secondary storagesystem 120B by issuing a write command to the secondary storage system120B (an arrow-headed line 1606).

The secondary storage system 120B stores the journal received as a writecommand from the primary storage system 120A in the area of thesecondary journal volume designated by the write command.

The secondary host 110B, by executing a journal reflection program 1624,reads a journal from the secondary journal volume area 627B, andrecovers data in the SVOL 626 (an arrow-headed line 1608).

The secondary journal group is managed by the secondary host 110B sothat the host 110B notifies information required for creating a requestfor journal transfer (information on journal volume for storage, etc.)of the primary host 110A. The area in which the reflection-completedjournal is stored is purged, thus enabling the use for storing a newjournal.

The journal volume switching in the embodiment is carried out in a waysimilar to the journal volume switching in the first embodiment.

[Features of the Data Processing System of the Present Invention inTerms of the Above Preferred Embodiments]

The above data processing system of the present invention is configuredsuch that a storage system executes journal acquisition/reflection andtransfer while a host or a storage system executes journal managementand copy status management. With the configuration, actual data transferfor data duplication between the primary site and the secondary site isexecuted via a fiber-optic cable between the storage systems. Thus, itis possible to minimize traffics in a general communication line betweenhosts, and it is also possible to improve copying performance since datatransfer can be performed in a high-speed line.

Further, the storage system has a function of writing a journal toanother storage system by using a write command, and a host reads thejournal for recovery. Thus, it is possible to realize data duplicationwithout giving any special functions to the storage system in thesecondary site.

Furthermore, a journal group has a plurality of journal volumes, journalvolumes for storage are switched, journal acquisition/transferoperations are executed in the primary site and journaltransfer/reflection operations in the secondary site for differentjournal volumes. Thus, it is possible to achieve load balancing onaccess to a journal volume. As a result, delays in volume reading andwriting caused by load concentration on a volume can be reduced, thusenabling improved system as a whole.

1.-15. (canceled)
 16. A data processing system, comprising: a primarysite which includes a first computer and a first storage systemconnected to said first computer, said first storage system having afirst logical volume for storing data sent from said first computer,said first logical volume related to at least one disk drive in saidfirst storage system; and a secondary site which includes a secondcomputer and a second storage system connected to said second computer,said second storage system having a second logical volume related to atleast one disk drive in said second storage system, said second logicalvolume forming a pair relationship of a remote copy process with saidfirst logical volume and storing data already stored in said firstlogical volume; wherein, said first storage system and said secondstorage system are connected to each other via a communication line;said first storage system records update history of data as a journal ina storage device stores update data to be stored in said first logicalvolume into at least one of third logical volumes, and transfers saidupdate data stored in said at least one of third logical volumes to saidsecond storage system via said communication line in such a way thatsaid second computer is not in a transport path of said transferredupdate data from said first storage system to said second storagesystem; said second storage system stores said transferred update datainto said second logical volume; and said at least one of said thirdlogical volumes is switched to another one of said third logical volumesduring said remote copy process.
 17. A data processing system accordingto claim 16, wherein said second storage system executes data recoverybased on said stored transferred update data.
 18. A data processingsystem according to claim 16, wherein said switching is made at a timeas designated by a user.
 19. A data processing system according to claim16, wherein said switching is executed at a time when transfer of thelogical volume in which the update data for transfer to said secondarysite is stored is completed.
 20. A data processing system according toclaim 16, wherein said transferred update data in said second storagesystem is stored in a plurality of logical volumes, and while the updatedata is transferred to a certain logical volume, a transfer-targetlogical volume is switched to another logical volume.
 21. A dataprocessing system according to claim 20, wherein said switching is madeat a time as designated by a user.
 22. A data processing systemaccording to claim 20, wherein said second storage system recovers databased on said stored transferred update data, and said switching is madeat a time when all logical volumes which store update data used forrecovery are recovered.
 23. A data processing system according to claim16, wherein said second storage system acquires information related toupdate data recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said update data.
 24. A data processing system according to claim23, wherein said update data recorded in a storage device of said firststorage system is stored in a plurality of logical volumes, a logicalvolume for storage is switched to another logical volume, while theupdate data is stored in a certain logical volume, and said switching ismade at a time when a command for requesting dispatch of said updatedata is received from said second storage system.
 25. A data processingsystem according to claim 23, wherein said transferred update data insaid second storage system is stored in a plurality of logical volumes,a transfer-target logical volume is switched to another logical volume,while the update data is transferred to a certain logical volume, andsaid switching is made at a time when said update data transfer isstarted at said first storage system.
 26. A data processing systemaccording to claim 16, wherein: said at least one of said third logicalvolumes is switched to said another one of said third logical volumes ateach time period.
 27. A data processing system according to claim 16,wherein: said at least one of said third logical volumes is switched tosaid another one of said third logical volumes if update data stored insaid at least one of said third logical volumes has been transferred.28. A data processing system according to claim 16, wherein: said atleast one of said third logical volumes is switched to said another oneof said third logical volumes if amount of update data stored in said atleast one of said third logical volumes is equal or over a value.
 29. Adata processing system according to claim 16, wherein: said secondstorage system stores said transferred update data into at least one offourth logical volumes and reads said stored update data from said atleast one of fourth logical volumes and writes said read update data tosaid second logical volume; and said at least one of said fourth logicalvolumes is switched to another one of said fourth logical volumes.
 30. Adata processing system according to claim 29, wherein: said at least oneof said fourth logical volumes is switched to said another one of saidfourth logical volumes if said update data stored in said at least oneof said fourth logical volumes has been written to said second logicalvolume.
 31. A data processing system according to claim 29, wherein:said at least one of said fourth logical volumes is switched to saidanother one of said fourth logical volumes if amount of update datastored in said at least one of said fourth logical volumes is equal orover a value
 32. A data processing system, comprising: a primary sitewhich includes a first computer and a first storage system connected tosaid first computer, said first storage system having a first logicalvolume for storing data sent from said first computer, said firstlogical volume related to at least one disk drive in said first storagesystem; and a secondary site which includes a second computer and asecond storage system connected to said second computer, said secondstorage system having a second logical volume related to at least onedisk drive in said second storage system, said second logical volumeforming a pair relationship of a remote copy process with said firstlogical volume and storing data already stored in said first logicalvolume; wherein, said first computer and said second computer areconnected to each other via a first communication line, said firststorage system and said second storage system are connected to eachother via a second communication line, said first storage system storesupdate data to be stored in said first logical volume into at least oneof third logical volumes, said first computer acquires informationrelated to said update data stored in said at least one of third logicalvolumes from said first storage system and transmits the information tosaid second computer via said first communication line, said firststorage system transfers said update data to said second storage systemvia said second communication line in such a way that said secondcomputer is not in a transport path of said transferred update data fromsaid first storage system to said second storage system, said secondstorage system stores the transferred update data into said secondlogical volume; and said at least one of said third logical volumes isswitched to another one of said third logical volumes during said remotecopy process.
 33. A data processing system according to claim 32,wherein said second storage system issues a command requesting saidfirst storage system to send said update data.
 34. A data processingsystem according to claim 32, wherein data recovery in said secondstorage system is executed by a recovery program to be executed on saidsecond computer based on said transferred update data.
 35. A dataprocessing system, comprising: a primary site which includes a firstcomputer and a first storage system connected to said first computer;and a secondary site which includes a second computer and a secondstorage system connected to said second computer; wherein, said firststorage system and said second storage system are connected to eachother via a communication line, said first storage system includes afirst storage controller and a first storage device, said first storagecontroller executes a journal acquisition program which records dataupdate history in said first storage device as a journal, and a journaltransfer program which transfers said journal to said second storagesystem via said communication line, said second storage system includesa second storage controller and a second storage device, said secondstorage control system executes a journal reflection program whichrecovers data based on a journal and a journal transfer program whichreceives said transferred journal from said first storage system, whensaid journal is being transferred from said first storage system to saidsecond storage system, said first storage controller, while said journalis being stored in a certain logical volume of said first storagesystem, switches a logical volume for storage to another logical volumeof said first storage device, and said second storage controller, whilesaid journal is being transferred to a certain logical volume of saidsecond storage device, switches a transfer-target logical volume toanother logical volume of said second storage device.
 36. A dataprocessing system, comprising: a primary site which includes a firstcomputer and a first storage system connected to said first computer;and a secondary site which includes a second computer and a secondstorage system connected to said second computer; wherein, said firststorage system and said second storage system are connected to eachother via a communication line; said first storage system records updatehistory of data as a journal in a storage device, and transfers saidjournal to said second storage system via said communication line; andsaid second storage system stores said transferred journal to a storagedevice; wherein said second storage system acquires information relatedto a journal recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said journal; and wherein said journal recorded in a storage deviceof said first storage system is stored in a plurality of logicalvolumes, a logical volume for storage is switched to another logicalvolume, while the journal is stored in a certain logical volume, andsaid switching is made at a time when a command for requesting dispatchof said journal is received from said second storage system.
 37. A dataprocessing system according to claim 36, wherein said second storagesystem executes data recovery based on said stored journal.
 38. A dataprocessing system, comprising: a primary site which includes a firstcomputer and a first storage system connected to said first computer;and a secondary site which includes a second computer and a secondstorage system connected to said second computer; wherein, said firststorage system and said second storage system are connected to eachother via a communication line; said first storage system records updatehistory of data as a journal in a storage device, and transfers saidjournal to said second storage system via said communication line; andsaid second storage system stores said transferred journal to a storagedevice; wherein said second storage system acquires information relatedto a journal recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said journal; and wherein said transferred journal in said secondstorage system is stored in a plurality of logical volumes, atransfer-target logical volume is switched to another logical volume,while the journal is transferred to a certain logical volume, and saidswitching is made at a time when said journal transfer is started atsaid first storage system.
 39. A data processing system according toclaim 38, wherein said second storage system executes data recoverybased on said stored journal.
 40. A data processing system, comprising:a first storage system, in a primary site, coupled to a first computerand having a first logical volume for storing data sent from said firstcomputer, said first logical volume related to at least one disk drivein said first storage system; and a second storage system, in asecondary site, coupled to a second computer and having a second logicalvolume related to at least one disk drive in said second storage system,said second logical volume forming a pair relationship of a remote copyprocess with said first logical volume and storing data already storedin said first logical volume; wherein said first storage system receivesupdate data sent from said host computer and stores said update datainto said first logical volume and transfers said update data to saidsecond storage system such a way that said second computer is not in atransport path of said transferred update data from said first storagesystem to said second storage system; wherein said second storage systemstores said transferred update data into at least one of third logicalvolumes and reads said stored update data from said at least one ofthird logical volumes and writes said read update data to said secondlogical volume; and said at least one of said third logical volumes isswitched to another one of said third logical volumes during said remotecopy process.
 41. A data processing system, comprising: a primary sitewhich includes a first computer and a first storage system connected tosaid first computer; and a secondary site which includes a secondcomputer and a second storage system connected to said second computer;wherein, said first storage system and said second storage system areconnected to each other via a communication line; said first storagesystem records update history of data as a journal in a storage device,and transfers said journal to said second storage system via saidcommunication line in such a way that said second computer is not in atransport path of said journal from said first storage system to saidsecond storage system; said second storage system stores saidtransferred journal to a storage device; said journal recorded in thestorage device of said first storage system is stored in a plurality oflogical volumes; and the journal is stored in a certain logical volume,a logical volume for storage is switched to another logical volume. 42.A data processing system according to claim 41, wherein said secondstorage system executes data recovery based on said stored journal. 43.A data processing system according to claim 41, wherein said switchingis made at a time as designated by a user.
 44. A data processing systemaccording to claim 41, wherein said switching is executed at a time whentransfer of the logical volume in which the target journal for transferto said secondary site is stored is completed.
 45. A data processingsystem according to claim 41, wherein said transferred journal in saidsecond storage system is stored in a plurality of logical volumes, andwhile the journal is transferred to a certain logical volume, atransfer-target logical volume is switched to another logical volume.46. A data processing system according to claim 45, wherein saidswitching is made at a time as designated by a user.
 47. A dataprocessing system according to claim 45, wherein said second storagesystem recovers data based on said stored journal, and said switching ismade at a time when all logical volumes which store a journal used forrecovery are recovered.
 48. A data processing system, comprising: aprimary site which includes a first computer and a first storage systemconnected to said first computer; and a secondary site which includes asecond computer and a second storage system connected to said secondcomputer; wherein, said first storage system and said second storagesystem are connected to each other via a communication line; said firststorage system records update history of data as a journal in a storagedevice, and transfers said journal to said second storage system viasaid communication line in such a way that said second computer is notin a transport path of said journal from said first storage system tosaid second storage system; said second storage system stores saidtransferred journal to a storage device; said second storage systemacquires information related to a journal recorded in said first storagesystem, and said second storage system issues a command requesting saidfirst storage system to send said journal; said journal recorded in astorage device of said first storage system is stored in a plurality oflogical volumes, a logical volume for storage is switched to anotherlogical volume, while the journal is stored in a certain logical volume,and said switching is made at a time when a command for requestingdispatch of said journal is received from said second storage system.49. A data processing system, comprising: a primary site which includesa first computer and a first storage system connected to said firstcomputer; and a secondary site which includes a second computer and asecond storage system connected to said second computer; wherein, saidfirst storage system and said second storage system are connected toeach other via a communication line; said first storage system recordsupdate history of data as a journal in a storage device, and transferssaid journal to said second storage system via said communication linein such a way that said second computer is not in a transport path ofsaid journal from said first storage system to said second storagesystem; said second storage system stores said transferred journal to astorage device; said second storage system acquires information relatedto a journal recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said journal; said transferred journal in said second storagesystem is stored in a plurality of logical volumes, a transfer-targetlogical volume is switched to another logical volume, while the journalis transferred to a certain logical volume, and said switching is madeat a time when said journal transfer is started at said first storagesystem.
 50. A data processing system, comprising: a primary site whichincludes a first computer and a first storage system connected to saidfirst computer, said first storage system having a first logical volumefor storing data sent from said first computer, said first logicalvolume related to at least one disk drive in said first storage system;and a secondary site which includes a second computer and a secondstorage system connected to said second computer, said second storagesystem having a second logical volume related to at least one disk drivein said second storage system, said second logical volume forming a pairrelationship of a remote copy process with said first logical volume andstoring data already stored in said first logical volume; wherein, saidfirst storage system and said second storage system are connected toeach other via a communication line, said first storage system includesa first storage controller and a first storage device, said firststorage controller stores update data to be stored in said first logicalvolume into at least one of third logical volumes, and transfers saidupdate data stored in said at least one of third logical volumes to saidsecond storage system via said communication line, said second storagesystem includes a second storage controller and a second storage device,said second storage control system receives said transferred update datafrom said first storage system and recovers data based on saidtransferred update data, when said update data is being transferred fromsaid first storage system to said second storage system, said firststorage controller, while said update data is being stored in a certainlogical volume of said first storage system, switches a logical volumefor storage to another logical volume of said first storage device, andsaid second storage controller, while said update data is beingtransferred to a certain logical volume of said second storage device,switches a transfer-target logical volume to another logical volume ofsaid second storage device.
 51. A data processing system, comprising: aprimary site which includes a first computer and a first storage systemconnected to said first computer, said first storage system having afirst logical volume for storing data sent from said first computer,said first logical volume related to at least one disk drive in saidfirst storage system; and a secondary site which includes a secondcomputer and a second storage system connected to said second computer,said second storage system having a second logical volume related to atleast one disk drive in said second storage system, said second logicalvolume forming a pair relationship of a remote copy process with saidfirst logical volume and storing data already stored in said firstlogical volume; wherein, said first storage system and said secondstorage system are connected to each other via a communication line;said first storage system stores update data to be stored in said firstlogical volume into at least one of third logical volumes, and transferssaid update data stored in said at least one of third logical volumes tosaid second storage system via said communication line; and said secondstorage system stores said transferred update data to a storage device;wherein said second storage system acquires information related toupdate data recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said update data; and wherein said update data recorded in astorage device of said first storage system is stored in a plurality oflogical volumes, a logical volume for storage is switched to anotherlogical volume, while the update data is stored in a certain logicalvolume, and said switching is made at a time when a command forrequesting dispatch of said update data is received from said secondstorage system.
 52. A data processing system according to claim 51,wherein said second storage system executes data recovery based on saidstored journal.
 53. A data processing system, comprising: a primary sitewhich includes a first computer and a first storage system connected tosaid first computer, said first storage system having a first logicalvolume for storing data sent from said first computer, said firstlogical volume related to at least one disk drive in said first storagesystem; and a secondary site which includes a second computer and asecond storage system connected to said second computer, said secondstorage system having a second logical volume related to at least onedisk drive in said second storage system, said second logical volumeforming a pair relationship of a remote copy process with said firstlogical volume and storing data already stored in said first logicalvolume; wherein, said first storage system and said second storagesystem are connected to each other via a communication line; said firststorage system stores update data to be stored in said first logicalvolume into at least one of third logical volumes, and transfers saidupdate data stored in said at least one of third logical volumes to saidsecond storage system via said communication line; and said secondstorage system stores said transferred update data to a storage device;wherein said second storage system acquires information related toupdate data recorded in said first storage system, and said secondstorage system issues a command requesting said first storage system tosend said update data; and wherein said transferred update data in saidsecond storage system is stored in a plurality of logical volumes, atransfer-target logical volume is switched to another logical volume,while the update data is transferred to a certain logical volume, andsaid switching is made at a time when said update data transfer isstarted at said first storage system.
 54. A data processing systemaccording to claim 53, wherein said second storage system executes datarecovery based on said stored journal.